PCI Express (Peripheral Component Interconnect Express), often abbreviated as PCIe, is a high-speed serial computer expansion bus standard. PCIe has high maximum system bus throughput, low I/O pin count and small physical footprint. PCIe has good performance-scaling for bus devices with a detailed error detection and reporting mechanism (Advanced Error Reporting (AER)). The PCIe electrical interface is used in a variety of other standards, such as ExpressCard, a laptop expansion card interface.
PCIe is generally based on point-to-point topology, with separate serial links connecting every device to the root complex (host). A PCIe bus link supports full-duplex communication between any two endpoints, with no inherent limitation on concurrent access across multiple endpoints.
PCIe communication is encapsulated in packets. The processes of packetizing and de-packetizing data and status-message traffic are handled by a transaction layer of the PCIe port.